Pairs of Segments

4000ms

524288K

Description:

Two segments $$$[l_1, r_1]$$$ and $$$[l_2, r_2]$$$ intersect if there exists at least one $$$x$$$ such that $$$l_1 \le x \le r_1$$$ and $$$l_2 \le x \le r_2$$$.

An array of segments $$$[[l_1, r_1], [l_2, r_2], \dots, [l_k, r_k]]$$$ is called beautiful if $$$k$$$ is even, and is possible to split the elements of this array into $$$\frac{k}{2}$$$ pairs in such a way that:

every element of the array belongs to exactly one of the pairs;
segments in each pair intersect with each other;
segments in different pairs do not intersect.

For example, the array $$$[[2, 4], [9, 12], [2, 4], [7, 7], [10, 13], [6, 8]]$$$ is beautiful, since it is possible to form $$$3$$$ pairs as follows:

the first element of the array (segment $$$[2, 4]$$$) and the third element of the array (segment $$$[2, 4]$$$);
the second element of the array (segment $$$[9, 12]$$$) and the fifth element of the array (segment $$$[10, 13]$$$);
the fourth element of the array (segment $$$[7, 7]$$$) and the sixth element of the array (segment $$$[6, 8]$$$).

As you can see, the segments in each pair intersect, and no segments from different pairs intersect.

You are given an array of $$$n$$$ segments $$$[[l_1, r_1], [l_2, r_2], \dots, [l_n, r_n]]$$$. You have to remove the minimum possible number of elements from this array so that the resulting array is beautiful.

Input:

The first line contains one integer $$$t$$$ ($$$1 \le t \le 1000$$$) — the number of test cases.

The first line of each test case contains one integer $$$n$$$ ($$$2 \le n \le 2000$$$) — the number of segments in the array. Then, $$$n$$$ lines follow, the $$$i$$$-th of them contains two integers $$$l_i$$$ and $$$r_i$$$ ($$$0 \le l_i \le r_i \le 10^9$$$) denoting the $$$i$$$-th segment.

Additional constraint on the input: the sum of $$$n$$$ over all test cases does not exceed $$$2000$$$.

Output:

For each test case, print one integer — the minimum number of elements you have to remove so that the resulting array is beautiful.

Sample Input:

Sample Output:

1
3
4

Note:

In the first test case of the example, it is enough to delete the $$$5$$$-th element of the array of segments. Then you get the array $$$[[2, 4], [9, 12], [2, 4], [7, 7], [10, 13], [6, 8]]$$$, which is beautiful.

In the second test case of the example, you can delete the $$$1$$$-st, $$$3$$$-rd and $$$4$$$-th element of the array. Then you get the array $$$[[2, 8], [5, 6]]$$$, which is beautiful.

In the third test case of the example, you have to delete the whole array.

Informação

Provedor Codeforces

Código CF1841D